Sahih Muslim Book 032, Hadith Number 6192.

Chapter : Kindness towards the friends of one's father and mother.

Ibn Dinar reported that a desert Arab met Abdullah b. 'Umar on the way to Mecca. 'Abdullah greeted him and mounted him upon the donkey on which he had been riding and gave him the turban that he had on his head. Ibn Dinar (further) reported: We said to him ('Abdullah b. 'Umar): May Allah do good to you, these are desert Arabs and they are satisfied even with meagre (things). Thereupon Abdullah said: His father was loved dearly by 'Umar b. Khattib and I heard Allah's Messenger (may peace be upon him) as saying: The finest act of goodness on the part of a son is to treat kindly the loved ones of his father.

Related Hadith(s)